Intense cramping a week before menstral - Implantation or menstral approaching? Or, contact obgyn ASAP?

I was at work and like my normal routine during my lunch hour I go to the gym and take thier 1hr high intensity spin class. While spinning and doing a hard climb I slowly start to cramp in my lower abdominal (very similar to those menstral cramps we all love!). But, I am thinking okay my period is about 4-7 days away and understood the cramps at the time as if maybe I am starting early this month. However, the pain increase to the point I started to have a look of death on my face and tried to stay with the class thinking to myself we'll this is bad I might not make it through the entire class. And, so I toughen up and continue to ride but at one point the pain was so intense i just got off the bike and ran upstair to the womens locker room and sat down thinking OMG what is this? I am talking cramping like never before enough that I had to ewxcuse myself from a class to handle the pain and make all the faces I need to until it goes away.. Could implantation cramping be that servere

Any kind of severe abdominal pain should really be checked out. If it's bad enough that it is impeding you then a visit to the doctor is not a bad idea. There are a lot of organs in the abdominal cavity, not just your uterus, and often bladder/bowel problems can give off the same kind of pain as menstrual cramps. There's also the possibility of an irritated appendix, or what they call a grumbling appendix, all which needs to be ruled out.